x.json2.decoder2: improve decode array (#22556)

vlib/x/json2/decoder2/decode.v

@@ -506,6 +506,30 @@ fn (mut decoder Decoder) decode_value[T](mut val T) ! {
 	} $else $if T is time.Time {
 	} $else $if T is $map {
 	} $else $if T is $array {
+		array_info := decoder.values_info[decoder.value_info_idx]
+
+		if array_info.value_kind == .array {
+			array_position := array_info.position
+			array_end := array_position + array_info.length
+
+			decoder.value_info_idx++
+			for {
+				if decoder.value_info_idx >= decoder.values_info.len {
+					break
+				}
+				value_info := decoder.values_info[decoder.value_info_idx]
+
+				if value_info.position + value_info.length >= array_end {
+					break
+				}
+
+				mut array_element := create_array_element(val)
+
+				decoder.decode_value(mut &array_element)!
+
+				val << array_element
+			}
+		}
 	} $else $if T is $struct {
 		mut nodes := []Node{}
 		// TODO: needs performance improvements
@@ -547,6 +571,10 @@ fn get_value_kind(value rune) ValueKind {
 	}
 }
 
+fn create_array_element[T](array []T) T {
+	return T{}
+}
+
 // decode_optional_value_in_actual_node decodes an optional value in a node.
 fn (mut decoder Decoder) decode_optional_value_in_actual_node[T](node Node, val ?T) T {
 	start := (node.key_pos + node.key_len) + 3
@@ -883,7 +911,7 @@ fn (mut decoder Decoder) fulfill_nodes(mut nodes []Node) {
 // string_buffer_to_generic_number converts a buffer of bytes (data) into a generic type T and
 // stores the result in the provided result pointer.
 // The function supports conversion to the following types:
-// - Signed integers: i8, i16, int, i64
+// - Signed integers: i8, i16, i32, i64
 // - Unsigned integers: u8, u16, u32, u64
 // - Floating-point numbers: f32, f64
 //

vlib/x/json2/decoder2/tests/bench.v

@@ -115,6 +115,22 @@ fn main() {
 
 	b.measure('old_json.decode(map[string]string, json_data1)!\n')
 
+	// array **********************************************************
+
+	println('\n***arrays***')
+
+	for i := 0; i < max_iterations; i++ {
+		_ := decoder2.decode[[]int]('[1, 2, 3, 4, 5, 6, 7, 8, 9, 0]')!
+	}
+
+	b.measure("decoder2.decode[[]int]('[1, 2, 3, 4, 5, 6, 7, 8, 9, 0]')!")
+
+	for i := 0; i < max_iterations; i++ {
+		_ := old_json.decode([]int, '[1, 2, 3, 4, 5, 6, 7, 8, 9, 0]')!
+	}
+
+	b.measure("old_json.decode([]int, '[1, 2, 3, 4, 5, 6, 7, 8, 9, 0]')!\n")
+
 	println('\n***simple types***')
 
 	// int **********************************************************

vlib/x/json2/decoder2/tests/decode_array_test.v

@@ -0,0 +1,5 @@
+import x.json2.decoder2 as json
+
+fn test_array_of_strings() {
+	assert json.decode[[]int]('[1, 2, 3]')! == [1, 2, 3]
+}